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Jean Legault, Chief Geophysicist at Geotech Ltd, discusses the impact of geophysical surveys on exploration for gold mineralization in Burkina Faso.

This presentation was recorded at PDAC 2020.



Jean Legault
Chief Geophysicist – Geotech Ltd


14 min

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Video Transcript

(gentle music)

<v ->Good afternoon, everybody.</v>

Welcome back to PDAC.

My name is James Lawton.

I’m the Chief Technology Officer for Seequent.

Before we get into this afternoon’s presentation,

just wanted to give a few words on what we’re doing

in terms of future directions across Seequent.

As you probably all know, or hopefully you know,

Seequent has three broad portfolios:

Geological, Geophysical, as well as Geo-technical.

And across all of those portfolios,

we’re deeply investing in each of them.

Especially in the geo-physical,

especially in the geological,

and wait a minute,

especially in the geo-technical as well.

So everywhere.

We’re also moving from just pure desktop software

into a hybrid model,

where you can run that software both on-premise,

on a desktop, and in the cloud.

And then moving towards pure cloud applications,

which we already have today.

As part of that overall movement or change

and some of the focus,

we’re also investing heavily in core building blocks.

The first of those is already out there,

Seequent ID,

providing a universal ID

that allows you to move seamlessly

from one spot in that workflow.

One piece of our portfolio to another,

without having to sign in again,

without having to worry

about whether you’re going to get access

to the data that you placed there.

The other things that we’re working on

are automatic ingesting of data,

so that you don’t have to have manual intervention.

You don’t have to worry

about where the data is coming from.

Bringing in to each of those elements.

We’re also working on automatic model updates,

so that when the data changes,

you get automatic model changes.

And that could be in Oasis motaj.

It could be in Voxy,

it could be in LeapFrog,

it could be in GeoStudio.

It could be in any single one of those.

So we’re also continuing to add more innovation

into the desktop products.

Adding more science,

more updates to the core algorithms,

to the core pieces of features, of functions.

We’re also investing heavily in performance.

And so as the products all start rolling out

in their next iteration in May,

you’re going to see dramatic performance improvements

across the board,

especially in Oasis montaj

and in LeapFrog.

And brand new stuff coming in,

in the GeoStudio arena as well.

Beyond that, we’re looking deeply and heavily

at data management overall.

So not only we’d want to move your data through,

what we also want to do is make sure it’s easy to find,

easy to access,

and again, just making it available,

wherever, however, whenever you’re doing anything.

Now, that’s enough for me.

What I’m going to do is pass you over

to our President presenter for today.

So I’d like to welcome Jean Legault,

the Chief Geophysicist at GeoTech.

<v ->Thank you, thank you.</v>

All right.
(audience applauding)

Yeah, hi everyone.

And it’s a pleasure to be here and thanks for coming.

I’m going to be presenting a talk

on the impact of geophysical surveys

on exploration for gold mineralization, Burkina Faso.

It’s actually, you can see there’s eight authors here

and I’m the very last one,

but I’ve presented it at,

the main author Nasreddine Bournas couldn’t be here today,

so I’m presenting it for you.

I presented it at,

we presented this paper at the SCG last year.

So I recognize the co-authors,

these are Toure, Balbone, Zagre, Ouedraogo

they’re all with the government of Burkina Faso in Buja.

and Kanita Khaled who’s now here at Seequent

and Alexander Prikhodko,

who was the previous User Data Processing manager

and the chief geophys and I’m the last speaker.

So here’s the outline of my talk,

basically, what this is,

it’s actually a showcase of a CET Lineament Analysis tool,

offered on the GeoSoft platform.

And it actually worked very, very well.

We’re very impressed with the software.

The whole paper is based on this.

If I can give you a kind of like a bit of a backstory.

We completed a large survey

for the government of Burkina Faso.

They have this beautiful dataset

and they want to be able to promote this around the world.

And they suggested, well,

why don’t we try to write a paper

on what are we going to do with such a massive dataset?

Well, let’s try the CET analysis and see what comes of it.

And this paper comes out of this.

I think you’d be very surprised

at how interesting the results were.

So I’m going to give an overview of Lineament Analysis

that is called LA.

Or we will present the Burkinian geophysical data.

And I’m going to show you the results

of that Lineament Analysis before concluding.

So obviously when you’ve got like large airborne datasets,

like we’re involved in, we collect data around the world.

This particular data set

is probably almost a half a million

where I collect data from over a period of decades.

You’ve got to be able to interpret these large data sets,

and they’re such large volumes and they’re very complicated.

And how do you do that in just a limited amount of time?

So there’s for us, our clients,

aren’t satisfied with just getting the geophysical data.

You better provide an adamant product.

Something that will add a little spark to your dataset

that will encourage explorers to invest in the country.

And so one of the easiest ways,

rather than toil over datasets for years on end

is to use these sediments semi-automated tools

and machine learning languages, algorithms, I should say.

And really this is how we’ve dealt with the big data.

And makes it faster, it’s more objective.

That’s the big thing is how do you remain consistent

in your approach to a dataset?

These semi-automated tools allow you to do that.

And so our clients are very pleased with that.

They, they responded that they liked

that aspect of the dataset.

And these results from,

the example I’m going to show you

is just a gold exploration application,

using these so-called heat maps.

So Lineament Analysis goes like this,

you’ve got these,

we all know that these Epithermal/Mesothermal

sheer hosted gold deposits are associated

with a hundreds of thermal alteration,

but they’re all structurally controlled.

We all know this.

And so the CET analysis is based on these premises.

You do a texture analysis,

then you do a ridge detection,

thinning and vectorization.

This is the basic steps.

And then we organize these into what they call heat maps.

And these are all to benefit, primarily, in this case,

gold exploration and targeting.

Like I said, these are all performed

on the CET analysis tool on the Oasis montaj platform.

Just very vaguely, I’m sure that Nasreddine

would do a much better job at explaining all of these,

but the Ridge detection is using log-Gabor wavelets.

We also look at orientation,

once you’ve got the Ridge detection,

you can apply different features,

to look for different aspects.

You can look for intersections of density,

but you can also look for orientation diversity.

So those are the two steps

based on these authors in their work.

This is the geology and Burkina Faso.

Primarily, through the middle of these purples,

represent these Eburian Granitoids

You’ve also got a Paleo-Proterozoic Basement

in yellow and green and through the middle.

On the west side, there’s Neo-Proterozoic Sedimentary Cover.

On the east side, there’s also a Cenozoic Terrains.

So the area in the middle is basically

what we’re focusing on.

This is where the gold mineralization is in Burkina Faso.

These are the overview of the gold mineralization

that is there.

You can see there’s a number of deposits.

It’s very important for gold.

And, but there are other types of mineralization,

zinc, copper.

It’s a very rich country.

But obviously it’s still a poor country.

And so well, they’re trying as best as they can

to promote exploration

using these EU and world bank funded geophysical programs.

This is before the 1990s, they didn’t,

and that’s not atypical.

There’s very little information,

very few sparse surveys

involving magnetics radiometrics and EM.

But starting in 1998, 99, CGG

formerly , produced the first part of the survey,

most of it on the Eastern border,

you can see there’s differences in resolution.

That’s where the shield areas or the focused area

and the sedimentary area has much smoother.

You can see that there’s a distinctive difference

between the two.

One is flown at one kilometer spacings

on the Western side,

and the other side is flown with a 500 meter spacings.

This is the block that we flew from 2015 to 2016,

represents about it,

I’m not sure how big the CGG block was,

but our block was about 150,000 line kilometers.

And we flew to that at 400 meters spacing

with five kilometer ties.

And then more recently, there is a Xcalibur completed.

So this is actually a high resolution image

of the magnetic map of Burkina Faso.

We don’t get to see a lot of these datasets very often,

but that’s what a full country coverage looks like

in Burkina Faso.

So now what?

We’ve got this data, what do we do with it?

Well, we know regionally

they have these known geological structures

that they’ve mapped along, which they find gold deposits

that are shown in white.

There there’s this,

the Western shear zone has gold deposits

and this eastern shear zone

called the Timberly-Dory Marking sheer zone.

Anyway, you can see that the gold deposits

are aligned along both.

And what did we do?

We just like, very simply we used the CET analysis

and came up with these lineaments.

So this is, it’s basically, semi-automated.

Here we have all the lineaments that are generated.

Now, what would we do?

Well, we just kind of like, just focus.

How did we get all of those?

This is very dense data.

And basically I’m showing you,

like an interpreter would have a hard time

coming up with this.

But it’s done semi-automatically, right?

This is what’s called a,

it’s an output of the CET program.

It’s called the Lineament Intersection Density Map.

So it’s showing you basically

where the computer’s calculated the largest density

of these lineaments.

And you can see the correlation with the gold.

There’s many of the gold deposits that are associated

with these high density intersections,

of course, but not all.

I mean, there are exceptions.

You can see there are exceptions

where in the warm colors

where the all gold deposits aren’t situated.

This is a different look,

that one was orientation density,

now we’re looking at orientation diversity.

So the diversity of lineaments

that were calculated within that space.

And now you actually see a much better correlation

with the non gold zones,

much better correlation.

And this is using a radius of influence of 20 kilometers.

So basically, looking at density,

think of it as a, just an area of an area of interest,

20 kilometers wide, how you generated these.

20 kilometers there’s the bottom of the scale.

It is on the bottom.

This is a different map.

If I kind of like, this is,

that was 20 kilometer density radius of influence.

This is five kilometers,

so much more focused.

And it’s actually surprising how much better you can see.

There’s much more correlation.

One thing that interested us too, though,

just on the Southeast side,

where you’ve got nicest density,

and these are areas that point to greater potential

in the Southeastern corner of the belt.

So if we just focus in this was called the Golden Y.

So the there’s kind of like a split in the structure.

And you can see how almost all of these gold deposits lie

within these influence.

And this is semi-automated

it’s like hours to perform on a dataset.

Just, you know, we also collected radiometrics.

So this is just a map of the radiometric image.

It’s very, very rich.

These countries are ideal for flying radiometrics,

looking for alteration mapping and so forth.

And that was basically my presentation.

Just to conclude, like we just showed,

we have a country wide map,

how can we quickly go through that map efficiently?

And with using the CET tool we found a method to do that.

And this is, anybody can perform it.

I mean, we obviously we played with it.

We’ve we applied this to regional scale.

We even applied this to grid scale surveys.

It’s a very, very useful tool.

And it’s a very economical tool,

it’s not overly costly, it’s very, very simple.

We we use it almost continuously.

We’re very, very pleased with the results.

And like I said, for the government of Burkina Faso,

what they were interested in was,

hey, listen, we’ve identified areas

where we know there’s mineralization.

We’ve got areas that have similar results

that are under explored,

these represent areas for exploration potential.

That’s the end of my presentation.

Thank you very much.

(audience clapping)